The invention relates, generally, to a touch input device and, more particularly, to an opto-matrix frame having early component degradation tracking and warning.
Coincident with the use of video displays has always been the problem of the man/machine interface. Traditionally, control of displayed information or cursors has been via a keyboard. Recently, however, a number of devices have been introduced which allow an operator to directly interact with the video display. These types of devices have included light pens, desk-type mouse controllers, or touch input devices such as a switch matrix or opto-electronic matrices. While generally switch-type overlays which are placed adjacent a video display are inexpensive to apply and utilize, they are generally susceptible to contact wear as well as distortion of the video information which is presented to the viewer, particularly in high usage environments. However, since opto-matrix schemes utilize light, which is generally in the infrared region, the switch matrix presented by the light beams is invisible to the viewer and, therefore, does not distort the video information displayed to the viewer and is not subject to wear in high usage environments. A number of schemes which utilize opto-matrix frames may be found in U.S. Pat. No. 4,267,443 "Photoelectric Input Apparatus", issued May 12, 1981 to Carroll et al; U.S. Pat. No. 4,243,879 "Touch Panel with Ambient Light Sampling", issued Jan. 6, 1981 to Carroll et al; and U.S. Pat. No. 3,764,813 "Coordinate Detection System", issued Oct. 9,1973 to Clement et al. These three schemes address problems inherent with opto-matrix devices such as increasing frame resolution without a corresponding increase in components, surrounding or ambient light compensation, or optimization of emitter/detector driving and detecting networks respectively.
Another problem inherent in opto-matrix frames is the detection of bad or marginal components which tend to indicate that a stylus hit has occurred. This may occur where an emitter or detector or circuitry associated therewith has failed thereby not producing or registering light with the result that the decoding circuitry sees the absence of light as a stylus hit. This therefore results in a false condition. Another problem is where devices degrade or there is a buildup of dirt and oils on the bezel or the face of the emitter or detector. Generally, this condition will cause increasing amounts of false readings or may be a prelude to component failures. Accordingly, it is desirable to have a scheme which keeps track of apparent component failure or of impending component degradation and failure. Additionally, it is also desirable to have a scheme which flags or registers these degradations of failures before or as close to the time of failure as is practicable. Such a scheme is taught by the present invention.
Accordingly, it is desirable to have and as an object of the present invention, an opto-matrix touch input device having fault detection, comprising a four-sided frame, optical emitters disposed in two adjacent sides of the frame, optical detectors disposed in the two sides of the frame opposite the emitters, a sampling device for sequentially sampling the light received by the detectors, a converter for converting the value of the light received by the detectors to a digital value and a processor connected to the converter for comparing the output of the detector prior to and/or during and/or after energization of a corresponding emitter, thereby deriving a signal manifesting either the absence or inadequacy of output of a detector thereby indicating a failed emitter and/or corresponding detector or components associated therewith or a marginal emitter and/or corresponding detector or components associated therewith.